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SECTION 2 DESCRIPTION
The ESP-400 is powered by a three-phase main transformer which combines with solid state control to provide volt-
amperes curve output characteristics required for plasma cutting (see figure 2-1). A three-phase full wave SCR and
diode bridge rectifier are used to convert the ac output current from the transformer to dc cutting current, and also control
the output current through the SCRs. A network of integrally-mounted capacitors and resistors provide transient and
high frequency voltage protection to the rectifier SCRs and diodes. Protection for the main transformer bridge rectifier
and the inductor is provided by over-temperature thermal switches which interrupt power in the event of an overheating
condition and automatically reset when the components have cooled to their normal operating temperature. Filtering
of the dc output current is provided by an inductor.
The solid state circuitry of the ESP-400 produces stable cutting current and eliminates changes in output current as
components heat up and/or if input line voltage changes within +10% of nominal. In addition, the control circuit has built-
in line voltage compensation, which corrects the output of the Power Source for various changes in the input line voltage.
This feature ensures consistency in cutting conditions even if line voltage changes. Actual load current and voltage
are indicated by an ammeter and voltmeter mounted on the front panel.
Connections for control functions from the Flow Control assembly are made from a 19-pin plug receptacle on the front
panel. This receptacle provides connection for auxiliary 115 volts out, remote current control.
The Power Source is designed for ease in moving and handling. Sufficient clearance and reinforcement at its base
permits lifting with a fork lift truck; or raising with a crane or hoist using the lifting rings in the top cover.
When moving the power source, always use both lifting rings in order to keep
the power source level, otherwise serious internal damage may occur.
2.3 Cool-Down Periods
The ESP-400 Power Source has two cool-down periods: 1) 100% duty @ 400 amperes (400 amperes may be applied
continuously without a cool-down period); 2) 50% duty - 1 hour base period @ 500 amperes (500 amperes may be
applied continuously for 30 minutes followed by a 30 minute cool-down period with fan motor running. This cool-down
period is proportionately less for shorter operating periods).
Output ratings are designed and based on an unobstructed supply of cooling
air flow over its internal components. DO NOT USE FILTERS ON THIS UNIT.
Periodically blow out dirt accumulations, using low pressure air.
2.4 Volt-Ampere Curves
The volt-ampere curves show the output voltage available at any given output current for the various current control
(or V ref signals from CNC control) settings. Values for settings other than those shown in figure 2-1, fall between the
Minimum and Maximum curves shown.
(40 paginas)
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